Bag, as a particular interest or area of expertise, is from 1964 and came from jazz jargon. It’s likely based on the notion of putting something in a bag, thus possessing it. Example: “Folk music is my bag, man.” It was a weekend hipster word that fell out of use in the 1970s.
Boggie originally referred to a style of early blues, short for boogie-woggie, used as early as 1928. By the 1960s, as a verb, it came to mean dancing to music with a heavy blues beat, then later dancing to any rock and roll. Soon “let’s boogie” as in “let’s go” was common baby boomer jargon.
Centering, as a concept in spirituality – to find balance or center in one’s awareness – became trendy in the late 1960s. Baby boomer guru Baba Ram Dass (aka Richard Alpert, LSD buddy of Tim Leary at Harvard) helped to popularize it in Be Here Now. It draws from Eastern religions and the concept of yin/yang. American “witch” culture – Wicca – also uses the idea: an effort to find balance amid a world of conflicting forces. In common jargon it came to mean “cool it, dude; find your comfortable spot, and watch all the s—pass by.”
Cop out has been around for a century. Originally it meant to take something for oneself – to steal or grab. By the 1930s, it was used to signify pleading guilty to a crime or taking a plea bargain, then evolved into backing down or surrendering. It was a short linguistic step in the 1960s for the phrase to signify taking the easy way out.
Hickey is a red welt, usually on the neck, given by an overzealous lover. It was a badge of honor for 1950s baby boomer teens who popularized and likely coined it. As the 1960s sexual revolution heated up, the word assumed an air of innocence and was used less often.
Split, meaning to leave, is beatnik slang, first recorded in 1954. It derived from the standard definition to divide up in pieces. “Let’s make like an amoeba and split, man.” It’s not believed to be a part of older black street slang or jazz. Also entering the vocabulary in the 1950s were split-level, split-screen, and split shift, all anathemas to beatniks.